Shoulder Implant Stem with Flexible Sidewall Segments
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Solution Overview
Problem
Existing shoulder joint prostheses face challenges in achieving secure fixation with minimal bone removal, maintaining range of motion, and ensuring immediate stability without cementing, especially in cases of bone loss or instability.
Innovation Solution
A humerus implant with a cup-shaped body and stem design, featuring flexible sidewall segments with locking fins and recesses for radial anchoring, and a key-slot connection for assembly, allowing for secure fixation and adaptation to different bone geometries without the need for cementing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a stem is used for fixation, then stability is improved, but bone removal increases
Solution Approach 1:
The cup-shaped body is divided into multiple flexible sidewall segments that can be independently deformed and positioned. This segmentation allows the implant to achieve stable fixation through distributed anchoring of individual segments rather than requiring a large stem, thereby reducing bone removal while maintaining stability.
Solution Approach 2:
The sidewalls of the cup-shaped body are made flexible to enable compression during insertion and subsequent expansion within the bone cavity. This flexibility allows the implant to adapt to the available bone space and achieve secure fixation without requiring extensive bone removal or a large stem structure.
2Strength
If cementing is used for fixation, then retention force is improved, but operation complexity increases
Solution Approach 1:
The implant achieves fixation through its own structural features (flexible sidewalls that expand and lock into place, locking fins that engage with bone) rather than requiring external cementing materials. The expansion mechanism itself generates the retention force, making the system self-sufficient and eliminating the need for additional cementing steps.
Solution Approach 2:
The cup-shaped body with curved sidewalls expands radially upon insertion, creating uniform contact pressure against the bone cavity walls. This curved geometry naturally distributes forces and enhances mechanical interlocking without requiring cement, simplifying the surgical procedure while maintaining strong retention.
3Adaptability or versatility
If multiple sidewall segments are used, then adaptability is improved, but device complexity increases
Solution Approach 1:
The cup-shaped body is divided into multiple flexible sidewall segments that can independently deform and adapt to the contours of the bone cavity. This segmentation provides adaptability to various bone geometries while keeping the overall structure as a single integrated component, avoiding the complexity of multiple separate parts.
Solution Approach 2:
Multiple sidewall segments are merged into a single cup-shaped body structure that functions as one unit. The segments are connected in such a way that they move and deform together, providing adaptability to different bone geometries while maintaining structural integrity and avoiding the need for complex assembly of multiple separate components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The implant achieves high retention force and stability, enabling immediate joint use with precise placement and orientation, and allows for adaptation to various bone structures, reducing insertion torque and facilitating easy replacement of prosthetic heads.
Implementation Method 1
A first type of sidewall segments preferably has a plurality of locking fins, which immediately anchor the cup shaped body within the bone. Due to the radial anchoring in the bone material, the fins cause a comparatively high pull out force of the implant.
Implementation Method 2
A second type of sidewall segments preferably has a structure of recesses and holes, which allow ingrowth of the bone. The recesses increase the pull out force of the cup shaped body, while the holes block rotation.
Implementation Method 3
The implant further comprises a stem to which the cup shaped body can directly be fixed. Due to the direct connection of the cup shaped body to the stem, the implant is a rigid unit after assembly.
Implementation Method 4
The fins have inclined leading surfaces to minimize insertion torque.
Data Source
AI summary
A humerus implant has a stem, cup shaped body and a locking adapter. The cup shaped body is locked to the stem by a key-slot mechanism. The cup shaped body has a center portion and a plurality of flexible first sidewall segments and second sidewall segments, with gaps between neighbored sidewall segments. The first sidewall segments have a plurality of locking fins while the second sidewall segments having a plurality of recesses and holes. The locking adapter has means for fixing the locking adapter to the cup shaped body and a locking ring for locking the sidewall segments into their final positions.